Questions tagged [swap-test]
For questions related to the "Swap test": a quantum algorithm whose purpose is to quantify the distance between two given quantum states.
12
questions
0
votes
1answer
36 views
Parameterized swap test and perfect swap test
Suppose one has parameterized a swap test by using an ansatz $U(\theta) = \exp(-i\theta \text{ CSWAP})$, and one tries to find an angle $\theta$ such that one can distinguish given two quantum states ...
1
vote
2answers
80 views
Confusion in computing the $1+|\langle\phi|\psi\rangle|^2$ term in the quantum swap test algorithm
I am having trouble understanding a particular step of the Swap-test algorithm.
As I am struggling with this for the past week, I thought I should ask here.
So, I get the procedure until right after ...
2
votes
1answer
141 views
Amplitude encoding: distinction between negative and positive real values
I want to encode two vectors into qubits and compute a distance between them that corresponds/is proportional to the euclidian distance of the real vectors.
The encoding I use is
A) qiskit ...
0
votes
0answers
31 views
Quantum check sample implementation
I've been trying to figure out how to create a simple circuit in Qiskit to create a check (cheque ) generation and verification as described in this paper.
I started with 3 qubits, first one with the ...
1
vote
1answer
83 views
How do you test a pair of unknown qubits for orthogonality with certainty?
If you want to check if a pair of unknown qubits are the same, a standard test is the controlled SWAP test. This gives a result of 0 with certainty if the states are the same and 1 with a 50% chance ...
3
votes
1answer
158 views
How to calculate inner product of quantum states with other method than swap test? [duplicate]
In connection to this question, I am wondering how to calculate value $\langle \psi|\phi \rangle$ for arbitrary quantum states $|\psi\rangle$ and $|\phi\rangle$.
A swap test is able to return only $|\...
2
votes
1answer
74 views
In the swap test, how is the final probability $P(0)$ calculated?
Does anyone know much about quantum dot product:
Lets say:
$$|\psi \rangle = \frac{|0\rangle_1|\overrightarrow{x_i}\rangle_2 + |1\rangle_1|\overrightarrow{x_j}\rangle_2}{\sqrt 2}$$
$$|\phi \rangle = \...
1
vote
1answer
42 views
In a Swap Test why is the control qubit influenced and aren't the target qubits altered?
I am in a study group learning about quantum computing using O'Reilly - Programming Quantum Computing. I'm a developer, not a physicist. :) I feel like my question is rudimentary but I can't seem to ...
10
votes
2answers
2k views
How and why does swap test works?
I am having some trouble understanding why a SWAP test would work. I meant I read that and understood the concepts as follows:
If the two input states are equal, the output register always results
in ...
7
votes
2answers
378 views
Distance calcluation between two vectors
In Quantum Machine Learning for data scientists, Page 34 gives an algorithm to calculate the distance between two classifical vectors. As mentioned in this question, it is not clear how the SwapTest ...
2
votes
3answers
560 views
Swap Test for vector difference - how are different sized inputs combined?
I'm working on a similar problem of that raised by Aman in Inner product of quantum states
Concerning the use of Swap Test for calculating the difference of two vectors.
An example of the original ...
3
votes
2answers
502 views
Can the SWAP test only compare registers with the same number of qubits?
I'm using the SWAP test circuit for implementing a qubit registers comparison
From the documentation I could find I've understood it can be applied to input qubits |$\alpha\rangle$ and |$\beta\...